Define the principle of conservation of linear momentum and deduce the law of conservation of linear momentum from it. a) Momentum is conserved when the net external force acting on a system is zero. b) Momentum is conserved when the net internal force acting on a system is zero. c) Momentum is conserved when the net external force acting on a system is not zero. d) Momentum is conserved when the net internal force acting on a system is not zero.
